Nick, that looks the same as the new Stihl one. Just a different colour I guess.
I've always filed by hand without a guide, it takes a while to get it right. Trial and error, just like most things I've learnt.
I saw this on Steve's site a while back.
<iframe width="560" height="315" src="http://www.youtube.com/embed/p57zA9OOjs0" frameborder="0" allowfullscreen></iframe>